Respiratory protection for healthcare workers and SARS-CoV-2: evidence is equivocal but does that matter?

So, a double blog day today! I couldn’t resist reading the latest statement from a UKHSA expert group on “The role of respirators and surgical masks in mitigating the transmission of SARS-CoV-2 in healthcare settings: an overview of evidence (2022)”, published yesterday, as soon as it hit my desk. “Equivocal” is a word that I try to avoid. It’s one of those ‘jargony’ and overly technical words that is best worded-around in my view. But for this, it’s about right. The evidence from well controlled clinical trials that respirators (FFP2/3 or N95s) offer superior protection to healthcare workers than surgical masks is equivocal (“open to more than one interpretation”). But does that matter? If we look to the physics of SARS-CoV-2 transmission, there is a risk that the type of small, virus-laden particles emitted by patients infected with SARS-CoV-2 could circumvent the level of protection provided by surgical masks. And so, it now seems reasonable to recommend FFP2/3 or N95s for healthcare workers caring for patients with SARS-CoV-2 (and influenza for that matter). However, given the uncertainty of the evidence base, as highlighted by this review, I can understand why some have decided to continue with a policy of surgical masks when caring for patients with SARS-CoV-2 infection in most settings.

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What the Cochrane “masks don’t work” review does (and does not) tell us

You may have seen some commentary and debate on a recently updated Cochrane review on physical interventions to interrupt the spread of respiratory viruses. I’m stepping into the debate only to clarify a few small points – and to provide an overview of what the review does (and does not) tell us. However, my firm advice is to read the review for yourself and come to your own conclusions.

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Finally, an RCT comparing N95s and medical masks to protect healthcare staff from COVID-19

Annals of Internal Medicine today published an RCT comparing the effectiveness of N95s vs. medical masks to protect healthcare staff from COVID-19. It’s a great piece of work, conducted over many years, and whilst the study has some important limitations, suggests that N95s don’t offer significantly increased protection than medical masks for healthcare staff caring for patients with confirmed or suspected COVID-19.

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Face coverings, surgical masks, and face filtering piece (FFP) respirators: what’s the difference and how are they tested?

You’ll all have seen wide variety of masks and face coverings worn in a wide (and often alarming!) variety of ways. Leaving aside the (in)correct wearing of masks, it’s useful to see some comparative data on the relative respiratory protection offered by different mask materials. This study, published years ago (pre COVID!), does just that.

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Considering the role of environmental contamination in the spread of COVID-19

We know that respiratory viruses can be spread through droplets, occasionally aerosols, and contact routes (see Figure 1). But what is the relative importance of these transmission routes for the SARS-CoV-2 virus, which causes COVID-19? A new pre-print paper published yesterday provides evidence that the stability of the SARS-CoV-2 coronavirus is broadly comparable to the ‘original’ SARS coronavirus (SARS-CoV-1) on dry surfaces and in aerosols. This paper supports an important role for dry surface contamination and aerosols in the spread of SARS-CoV-2, and suggests that improved environmental persistence isn’t the key to the relative success of SARS-CoV-2 over SARS-CoV-1.

Figure 1: Transmission routes of respiratory viruses (from this review article).

covid transmission routes

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